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-rw-r--r--lib/scatterlist.c281
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diff --git a/lib/scatterlist.c b/lib/scatterlist.c
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1/*
2 * Copyright (C) 2007 Jens Axboe <jens.axboe@oracle.com>
3 *
4 * Scatterlist handling helpers.
5 *
6 * This source code is licensed under the GNU General Public License,
7 * Version 2. See the file COPYING for more details.
8 */
9#include <linux/module.h>
10#include <linux/scatterlist.h>
11
12/**
13 * sg_next - return the next scatterlist entry in a list
14 * @sg: The current sg entry
15 *
16 * Description:
17 * Usually the next entry will be @sg@ + 1, but if this sg element is part
18 * of a chained scatterlist, it could jump to the start of a new
19 * scatterlist array.
20 *
21 **/
22struct scatterlist *sg_next(struct scatterlist *sg)
23{
24#ifdef CONFIG_DEBUG_SG
25 BUG_ON(sg->sg_magic != SG_MAGIC);
26#endif
27 if (sg_is_last(sg))
28 return NULL;
29
30 sg++;
31 if (unlikely(sg_is_chain(sg)))
32 sg = sg_chain_ptr(sg);
33
34 return sg;
35}
36EXPORT_SYMBOL(sg_next);
37
38/**
39 * sg_last - return the last scatterlist entry in a list
40 * @sgl: First entry in the scatterlist
41 * @nents: Number of entries in the scatterlist
42 *
43 * Description:
44 * Should only be used casually, it (currently) scans the entire list
45 * to get the last entry.
46 *
47 * Note that the @sgl@ pointer passed in need not be the first one,
48 * the important bit is that @nents@ denotes the number of entries that
49 * exist from @sgl@.
50 *
51 **/
52struct scatterlist *sg_last(struct scatterlist *sgl, unsigned int nents)
53{
54#ifndef ARCH_HAS_SG_CHAIN
55 struct scatterlist *ret = &sgl[nents - 1];
56#else
57 struct scatterlist *sg, *ret = NULL;
58 unsigned int i;
59
60 for_each_sg(sgl, sg, nents, i)
61 ret = sg;
62
63#endif
64#ifdef CONFIG_DEBUG_SG
65 BUG_ON(sgl[0].sg_magic != SG_MAGIC);
66 BUG_ON(!sg_is_last(ret));
67#endif
68 return ret;
69}
70EXPORT_SYMBOL(sg_last);
71
72/**
73 * sg_init_table - Initialize SG table
74 * @sgl: The SG table
75 * @nents: Number of entries in table
76 *
77 * Notes:
78 * If this is part of a chained sg table, sg_mark_end() should be
79 * used only on the last table part.
80 *
81 **/
82void sg_init_table(struct scatterlist *sgl, unsigned int nents)
83{
84 memset(sgl, 0, sizeof(*sgl) * nents);
85#ifdef CONFIG_DEBUG_SG
86 {
87 unsigned int i;
88 for (i = 0; i < nents; i++)
89 sgl[i].sg_magic = SG_MAGIC;
90 }
91#endif
92 sg_mark_end(&sgl[nents - 1]);
93}
94EXPORT_SYMBOL(sg_init_table);
95
96/**
97 * sg_init_one - Initialize a single entry sg list
98 * @sg: SG entry
99 * @buf: Virtual address for IO
100 * @buflen: IO length
101 *
102 **/
103void sg_init_one(struct scatterlist *sg, const void *buf, unsigned int buflen)
104{
105 sg_init_table(sg, 1);
106 sg_set_buf(sg, buf, buflen);
107}
108EXPORT_SYMBOL(sg_init_one);
109
110/*
111 * The default behaviour of sg_alloc_table() is to use these kmalloc/kfree
112 * helpers.
113 */
114static struct scatterlist *sg_kmalloc(unsigned int nents, gfp_t gfp_mask)
115{
116 if (nents == SG_MAX_SINGLE_ALLOC)
117 return (struct scatterlist *) __get_free_page(gfp_mask);
118 else
119 return kmalloc(nents * sizeof(struct scatterlist), gfp_mask);
120}
121
122static void sg_kfree(struct scatterlist *sg, unsigned int nents)
123{
124 if (nents == SG_MAX_SINGLE_ALLOC)
125 free_page((unsigned long) sg);
126 else
127 kfree(sg);
128}
129
130/**
131 * __sg_free_table - Free a previously mapped sg table
132 * @table: The sg table header to use
133 * @free_fn: Free function
134 *
135 * Description:
136 * Free an sg table previously allocated and setup with __sg_alloc_table().
137 *
138 **/
139void __sg_free_table(struct sg_table *table, sg_free_fn *free_fn)
140{
141 struct scatterlist *sgl, *next;
142
143 if (unlikely(!table->sgl))
144 return;
145
146 sgl = table->sgl;
147 while (table->orig_nents) {
148 unsigned int alloc_size = table->orig_nents;
149 unsigned int sg_size;
150
151 /*
152 * If we have more than SG_MAX_SINGLE_ALLOC segments left,
153 * then assign 'next' to the sg table after the current one.
154 * sg_size is then one less than alloc size, since the last
155 * element is the chain pointer.
156 */
157 if (alloc_size > SG_MAX_SINGLE_ALLOC) {
158 next = sg_chain_ptr(&sgl[SG_MAX_SINGLE_ALLOC - 1]);
159 alloc_size = SG_MAX_SINGLE_ALLOC;
160 sg_size = alloc_size - 1;
161 } else {
162 sg_size = alloc_size;
163 next = NULL;
164 }
165
166 table->orig_nents -= sg_size;
167 free_fn(sgl, alloc_size);
168 sgl = next;
169 }
170
171 table->sgl = NULL;
172}
173EXPORT_SYMBOL(__sg_free_table);
174
175/**
176 * sg_free_table - Free a previously allocated sg table
177 * @table: The mapped sg table header
178 *
179 **/
180void sg_free_table(struct sg_table *table)
181{
182 __sg_free_table(table, sg_kfree);
183}
184EXPORT_SYMBOL(sg_free_table);
185
186/**
187 * __sg_alloc_table - Allocate and initialize an sg table with given allocator
188 * @table: The sg table header to use
189 * @nents: Number of entries in sg list
190 * @gfp_mask: GFP allocation mask
191 * @alloc_fn: Allocator to use
192 *
193 * Notes:
194 * If this function returns non-0 (eg failure), the caller must call
195 * __sg_free_table() to cleanup any leftover allocations.
196 *
197 **/
198int __sg_alloc_table(struct sg_table *table, unsigned int nents, gfp_t gfp_mask,
199 sg_alloc_fn *alloc_fn)
200{
201 struct scatterlist *sg, *prv;
202 unsigned int left;
203
204#ifndef ARCH_HAS_SG_CHAIN
205 BUG_ON(nents > SG_MAX_SINGLE_ALLOC);
206#endif
207
208 memset(table, 0, sizeof(*table));
209
210 left = nents;
211 prv = NULL;
212 do {
213 unsigned int sg_size, alloc_size = left;
214
215 if (alloc_size > SG_MAX_SINGLE_ALLOC) {
216 alloc_size = SG_MAX_SINGLE_ALLOC;
217 sg_size = alloc_size - 1;
218 } else
219 sg_size = alloc_size;
220
221 left -= sg_size;
222
223 sg = alloc_fn(alloc_size, gfp_mask);
224 if (unlikely(!sg))
225 return -ENOMEM;
226
227 sg_init_table(sg, alloc_size);
228 table->nents = table->orig_nents += sg_size;
229
230 /*
231 * If this is the first mapping, assign the sg table header.
232 * If this is not the first mapping, chain previous part.
233 */
234 if (prv)
235 sg_chain(prv, SG_MAX_SINGLE_ALLOC, sg);
236 else
237 table->sgl = sg;
238
239 /*
240 * If no more entries after this one, mark the end
241 */
242 if (!left)
243 sg_mark_end(&sg[sg_size - 1]);
244
245 /*
246 * only really needed for mempool backed sg allocations (like
247 * SCSI), a possible improvement here would be to pass the
248 * table pointer into the allocator and let that clear these
249 * flags
250 */
251 gfp_mask &= ~__GFP_WAIT;
252 gfp_mask |= __GFP_HIGH;
253 prv = sg;
254 } while (left);
255
256 return 0;
257}
258EXPORT_SYMBOL(__sg_alloc_table);
259
260/**
261 * sg_alloc_table - Allocate and initialize an sg table
262 * @table: The sg table header to use
263 * @nents: Number of entries in sg list
264 * @gfp_mask: GFP allocation mask
265 *
266 * Description:
267 * Allocate and initialize an sg table. If @nents@ is larger than
268 * SG_MAX_SINGLE_ALLOC a chained sg table will be setup.
269 *
270 **/
271int sg_alloc_table(struct sg_table *table, unsigned int nents, gfp_t gfp_mask)
272{
273 int ret;
274
275 ret = __sg_alloc_table(table, nents, gfp_mask, sg_kmalloc);
276 if (unlikely(ret))
277 __sg_free_table(table, sg_kfree);
278
279 return ret;
280}
281EXPORT_SYMBOL(sg_alloc_table);